if i have understand correctly the input current sorce delivers 20ma ? and that is split up by the input mosfets to 10ma each?...cuz i have just read mark finnis "cloning manual" where he matches his input mosfet att 20ma each..that must be wrong??
Match devices at the current that you intend to use in the circuit. I'm relying on memory, but I believe that you're correct--the front end of an Aleph runs at 20mA for the pair, hence 10mA each device. So you should test them at 10mA.
What do you guys think about using low-level dual mosfets for an input stage. It looks like a TO-39 can w/ six leads. I think I read in an old Audio Electronics mag that Erno Borbley uses these in the input stage of his amps. It negated the need for matching since it's on the same chip. Any ideas on this??
Are these MOSFET's from Linear Systems? In which case, last time I checked they did not have the power rating to suit my taste. For low power stuff, consider using JFET's which probably perform better (unless your circuit is sensitive to input leakage current or you need more quiescent current before device saturation).
What are the names of the units you mention?
You can find a list of devices used by Borbely at his website http://www.borbely.com. Check out schematics and note heavy use of cascoding -- sometimes with J-FET's other times with FETs (when he needs more power dissipation?)
In my humble opinion, I think his designs have not changed much from what he published in Audio Electronics around 1990, but I am perhaps being a little cynical.